﻿/*
Stockfish, a UCI chess playing engine derived from Glaurung 2.1
Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
Copyright (C) 2008-2014 Marco Costalba, Joona Kiiski, Tord Romstad

Stockfish is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

Stockfish is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/


#include <algorithm> // For std::count
#include <cassert>

#include "movegen.h"
#include "search.h"
#include "thread.h"
#include "uci.h"
#include "open_book.h"
// #include "syzygy/tbprobe.h"

ThreadPool Threads; // Global object

/// Thread constructor launches the thread and then waits until it goes to sleep
/// in idle_loop().

Thread::Thread() {

	resetCalls = exit = false;
	maxPly = callsCnt = 0;
	tbHits = 0;
	idx = Threads.size(); // Start from 0

	std::unique_lock<Mutex> lk(mutex);
	searching = true;
	nativeThread = std::thread(&Thread::idle_loop, this);
	sleepCondition.wait(lk, [&] { return !searching; });
}


/// Thread destructor waits for thread termination before returning

Thread::~Thread() {

	mutex.lock();
	exit = true;
	sleepCondition.notify_one();
	mutex.unlock();
	nativeThread.join();
}


/// Thread::wait_for_search_finished() waits on sleep condition
/// until not searching

void Thread::wait_for_search_finished() {

	std::unique_lock<Mutex> lk(mutex);
	sleepCondition.wait(lk, [&] { return !searching; });
}


/// Thread::wait() waits on sleep condition until condition is true

void Thread::wait(std::atomic_bool& condition) {

	std::unique_lock<Mutex> lk(mutex);
	sleepCondition.wait(lk, [&] { return bool(condition); });
}


/// Thread::start_searching() wakes up the thread that will start the search

void Thread::start_searching(bool resume) {

	std::unique_lock<Mutex> lk(mutex);

	if (!resume)
		searching = true;

	sleepCondition.notify_one();
}


/// Thread::idle_loop() is where the thread is parked when it has no work to do

void Thread::idle_loop() {

	WinProcGroup::bindThisThread(idx);

	while (!exit)
	{
		std::unique_lock<Mutex> lk(mutex);

		searching = false;

		while (!searching && !exit)
		{
			sleepCondition.notify_one(); // Wake up any waiting thread
			sleepCondition.wait(lk);
		}

		lk.unlock();

		if (!exit)
			search();
	}
}


/// ThreadPool::init() creates and launches requested threads that will go
/// immediately to sleep. We cannot use a constructor because Threads is a
/// static object and we need a fully initialized engine at this point due to
/// allocation of Endgames in the Thread constructor.

void ThreadPool::init() {

	push_back(new MainThread());
	read_uci_options();
}


/// ThreadPool::exit() terminates threads before the program exits. Cannot be
/// done in destructor because threads must be terminated before deleting any
/// static objects while still in main().

void ThreadPool::exit() {

	while (size())
		delete back(), pop_back();
}


/// ThreadPool::read_uci_options() updates internal threads parameters from the
/// corresponding UCI options and creates/destroys threads to match requested
/// number. Thread objects are dynamically allocated.

void ThreadPool::read_uci_options() {

	size_t requested = Options["Threads"];

	assert(requested > 0);

	while (size() < requested)
		push_back(new Thread());

	while (size() > requested)
		delete back(), pop_back();
}


/// ThreadPool::nodes_searched() returns the number of nodes searched

uint64_t ThreadPool::nodes_searched() const {

	uint64_t nodes = 0;
	for (Thread* th : *this)
		nodes += th->rootPos.nodes_searched();
	return nodes;
}


/// ThreadPool::tb_hits() returns the number of TB hits

uint64_t ThreadPool::tb_hits() const {

	uint64_t hits = 0;
	for (Thread* th : *this)
		hits += th->tbHits;
	return hits;
}


/// ThreadPool::start_thinking() wakes up the main thread sleeping in idle_loop()
/// and starts a new search, then returns immediately.

void ThreadPool::start_thinking(Position& pos, StateListPtr& states,
	const Search::LimitsType& limits) {

	main()->wait_for_search_finished();

	Search::Signals.stopOnPonderhit = Search::Signals.stop = false;
	Search::Limits = limits;
	Search::RootMoves rootMoves;

	for (const auto& m : MoveList<LEGAL>(pos))
		if (limits.searchmoves.empty()
			|| std::count(limits.searchmoves.begin(), limits.searchmoves.end(), m))
			rootMoves.push_back(Search::RootMove(m));

	if (!rootMoves.empty()) {
#ifdef USE_OPENBOOK		// Tablebases::filter_root_moves(pos, rootMoves);
		if (limits.infinite == 0) {
			if (Search::Is_Have_Book_Move(pos, rootMoves)) {
				return;
			}
		}
#endif
	}

	// After ownership transfer 'states' becomes empty, so if we stop the search
	// and call 'go' again without setting a new position states.get() == NULL.
	assert(states.get() || setupStates.get());

	if (states.get())
		setupStates = std::move(states); // Ownership transfer, states is now empty

	StateInfo tmp = setupStates->back();

	for (Thread* th : Threads)
	{
		th->maxPly = 0;
		th->tbHits = 0;
		th->rootDepth = DEPTH_ZERO;
		th->rootMoves = rootMoves;
		th->rootPos.set(pos.fen(), &setupStates->back(), th); // th->rootPos.set(pos.fen(), pos.is_chess960(), &setupStates->back(), th);
	}

	setupStates->back() = tmp; // Restore st->previous, cleared by Position::set()

	main()->start_searching();
}


